A Botany byelection, following the impending resignation of Jami-Lee Ross, would be a public judgment on that issue.
Politics is of course in any case a tough business - and if National's private polling is telling them, as Jami-Lee Ross has indicated, that Simon Bridges has failed to fire, then it is only a matter of time before they pull the trigger. But before they do so, they should perhaps pause and reflect.
The most important question they must address is - what has changed since they elected Bridges as leader? They had every chance to survey the available options last time round, and no new options have presented themselves in the meantime. If Bridges was the best choice less than a year ago, who has emerged to lead them to a different conclusion this time?
With all due respect to Judith Collins or Paula Bennett or Mark Mitchell or Amy Adams, there is no obvious answer to that question - but it gets a little more complicated. Politicians are able to persuade themselves of almost anything - so someone who was rejected last time might suddenly seem to be the answer to their prayers now. The danger is that such a judgment would not be made in a vacuum but would be driven primarily by the need to find someone who was not Simon Bridges - with the result that someone who seemed unqualified, even unelectable, last time might suddenly seem the right choice on the simple ground that he or she was not the current leader with his admitted failings.
National could, in other words, all too easily make a decision for negative rather than positive reasons. They could end up with someone who does not share Bridges' shortcomings (or, for that matter, his strengths) but who has a different (but equally, or even more, damaging) set of limitations.
In the absence of any immediately compelling successor, a fresh start could simply mean a set of new and even more intractable difficulties - a moment's thought and a consideration of the most likely contenders will quickly establish what they could turn out to be. The temptation would be to overlook what was previously seen as a disqualification in the make-up of someone who had earlier been found wanting.
The lesson to draw is this. As Labour in earlier times well knows, a political party that is having difficulty engaging with the voters should not imagine that changing the leader will solve the problem - and Jacinda Arderns do not grow on trees. It would do better to look at itself - at its record in government, at its own shortcomings, at what it is seen to stand for, at its understanding (or lack of it) of the issues facing the country.
Simon Bridges may not have been able to resolve overnight the problems that led to National's election defeat - but he at least understands by now that a defeat is what it was. Supporting the leader, rather than changing him, may be National's best chance of reversing that result next time.